Claus has a point, it pains me to say.
But I think any communications in that regard should be done via PM. Send it to the person getting ripped off if you want, but I don't feel that communication should be in the public view.
We're all responsible for ourselves here. If I get ripped off on the price of something, it's because I failed to do my research. If someone else gets ripped off, it's because the failed to do theirs.
Howevfer, I don't think offers should be made in the public forums either. I think a list price should be displayed and offers and counter offers should be made via PMs.